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Development of protective inflammation and cell-mediated immunity against Cryptococcus neoformans after exposure to hyphal mutants. mBio 2015; 6:e01433-15. [PMID: 26443458 PMCID: PMC4611043 DOI: 10.1128/mbio.01433-15] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Morphological switch is tightly coupled with the pathogenesis of many dimorphic fungal pathogens. Cryptococcus neoformans, the major causative agent of cryptococcal meningitis, mostly presents as the yeast form but is capable of switching to the hyphal form. The filamentous form has long been associated with attenuated virulence, yet the underlying mechanism remains elusive. We previously identified the master regulator Znf2 that controls the yeast-to-hypha transition in Cryptococcus. Activation of Znf2 promotes hyphal formation and abolishes fungal virulence in vivo. Here we demonstrated that the cryptococcal strain overexpressing ZNF2 elicited strong and yet temporally confined proinflammatory responses in the early stage of infection. In contrast, exacerbated inflammation in mice infected with the wild-type (WT) strain showed that they were unable to control the infection. Animals inoculated with this filamentous Cryptococcus strain had fewer pulmonary eosinophils and CD11c(+) CD11b(+) cells than animals inoculated with WT yeast. Moreover, mice infected with this strain developed protective Th1- or Th17-type T cell responses. These findings suggest that the virulence attenuation of the filamentous form is likely due to its elicitation of protective host responses. The antivirulence effect of Znf2 was independent of two previously identified factors downstream of Znf2. Interestingly, mucosal immunizations with high doses of ZNF2-overexpressing cells, either in the live or heat-killed form, offered 100% protection to the host from a subsequent challenge with the otherwise lethal clinical strain H99. Our results demonstrate that heat-resistant cellular components presented in cryptococcal cells with activated ZNF2 elicit protective host immune responses. These findings could facilitate future research on novel immunological therapies. IMPORTANCE Cryptococcal meningitis is one of the leading causes of death among AIDS patients. This disease presents a severe threat to public health. The current antifungal regimens are unsatisfactory in controlling or clearing the pathogen Cryptococcus neoformans. Immunotherapies and/or vaccines could be a promising approach to prevent or manage this deadly disease. However, the lack of understanding of host-pathogen interactions during cryptococcal infection greatly hampers the development of effective immunotherapies. In this study, we discovered that inoculation of cryptococcal cells with activated Znf2, a morphogenesis regulator and an antivirulence factor, could shift the host pathological Th2 responses to the protective Th1 or Th17 responses. Importantly, we discovered that vaccination with either the viable or heat-killed form of ZNF2-overexpressing cells protected animals from the otherwise lethal infection by the highly virulent clinical strain. Our study suggests that the fungal cellular component(s) of the ZNF2-overexpressing strain may provide potential vaccine candidate(s) for controlling the fatal disease.
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Kwon-Chung KJ, Fraser JA, Doering TL, Wang Z, Janbon G, Idnurm A, Bahn YS. Cryptococcus neoformans and Cryptococcus gattii, the etiologic agents of cryptococcosis. Cold Spring Harb Perspect Med 2014; 4:a019760. [PMID: 24985132 PMCID: PMC4066639 DOI: 10.1101/cshperspect.a019760] [Citation(s) in RCA: 312] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cryptococcus neoformans and Cryptococcus gattii are the two etiologic agents of cryptococcosis. They belong to the phylum Basidiomycota and can be readily distinguished from other pathogenic yeasts such as Candida by the presence of a polysaccharide capsule, formation of melanin, and urease activity, which all function as virulence determinants. Infection proceeds via inhalation and subsequent dissemination to the central nervous system to cause meningoencephalitis. The most common risk for cryptococcosis caused by C. neoformans is AIDS, whereas infections caused by C. gattii are more often reported in immunocompetent patients with undefined risk than in the immunocompromised. There have been many chapters, reviews, and books written on C. neoformans. The topics we focus on in this article include species description, pathogenesis, life cycle, capsule, and stress response, which serve to highlight the specializations in virulence that have occurred in this unique encapsulated melanin-forming yeast that causes global deaths estimated at more than 600,000 annually.
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Affiliation(s)
- Kyung J Kwon-Chung
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - James A Fraser
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Tamara L Doering
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Zhou Wang
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Guilhem Janbon
- Unité Biologie et Pathogénicité Fongiques, Institut Pasteur, 75015 Paris, France
| | - Alexander Idnurm
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri, Kansas City, Missouri 64110
| | - Yong-Sun Bahn
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
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Lester SJ, Malik R, Bartlett KH, Duncan CG. Cryptococcosis: update and emergence of Cryptococcus gattii. Vet Clin Pathol 2011; 40:4-17. [PMID: 21244455 DOI: 10.1111/j.1939-165x.2010.00281.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cryptococcosis is a fungal disease that occurs throughout the world. Recent reclassification of Cryptococcus species along with a change in the distribution pattern has prompted reevaluation of the organism and the diseases caused by this pathogen. This review highlights the emergence of Cryptococcus gattii as a primary pathogen in North America and summarizes our current understanding of the disease in mammals and birds.
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Pettit RK, Repp KK, Hazen KC. Temperature affects the susceptibility ofCryptococcus neoformansbiofilms to antifungal agents. Med Mycol 2010. [DOI: 10.3109/13693780903136879] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Upadhyay SK, Shankar J, Singh Y, Basir SF, Madan T, Sarma PU. Expressed sequence tags of Aspergillus fumigatus: Extension of catalogue and their evaluation as putative drug targets and/or diagnostic markers. Indian J Clin Biochem 2009; 24:131-6. [PMID: 23105821 DOI: 10.1007/s12291-009-0024-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Aspergillus fumigatus a fungal pathogen is implicated in a spectrum of allergic and invasive disorders in humans. Validation of transcriptome of pathogen is essential for understanding its virulence mechanism and to identify new therapeutic targets/diagnostic markers. In order to rapidly identify genes of Aspergillus fumigatus we adopted sequencing of cDNA clones. Our earlier effort has lead to identification of 68 expressed sequence tags of Aspergillus fumigatus. Present study describes 52 more expressed sequence tags generated by sequencing 200 phage clones of a non-normalized cDNA library. One of the cDNA clones comprised of the complete coding region for tetratricopeptide repeat domain protein gene. Various homology search algorithms were employed to assign functions to expressed sequence tags coding for hypothetical proteins, and relevance of these expressed sequence tags or their protein products as drug targets/diagnostic markers was examined by searching for homologues in fungi and human.
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Affiliation(s)
- Santosh Kumar Upadhyay
- Institute of Genomics and Integrative Biology, Mall road, Delhi, 110007 India ; Department of Biosciences, Jamia Millia Islamia, New Delhi, 110025 India
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Gillespie JJ, Beier MS, Rahman MS, Ammerman NC, Shallom JM, Purkayastha A, Sobral BS, Azad AF. Plasmids and rickettsial evolution: insight from Rickettsia felis. PLoS One 2007; 2:e266. [PMID: 17342200 PMCID: PMC1800911 DOI: 10.1371/journal.pone.0000266] [Citation(s) in RCA: 176] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Accepted: 02/08/2007] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND The genome sequence of Rickettsia felis revealed a number of rickettsial genetic anomalies that likely contribute not only to a large genome size relative to other rickettsiae, but also to phenotypic oddities that have confounded the categorization of R. felis as either typhus group (TG) or spotted fever group (SFG) rickettsiae. Most intriguing was the first report from rickettsiae of a conjugative plasmid (pRF) that contains 68 putative open reading frames, several of which are predicted to encode proteins with high similarity to conjugative machinery in other plasmid-containing bacteria. METHODOLOGY/PRINCIPAL FINDINGS Using phylogeny estimation, we determined the mode of inheritance of pRF genes relative to conserved rickettsial chromosomal genes. Phylogenies of chromosomal genes were in agreement with other published rickettsial trees. However, phylogenies including pRF genes yielded different topologies and suggest a close relationship between pRF and ancestral group (AG) rickettsiae, including the recently completed genome of R. bellii str. RML369-C. This relatedness is further supported by the distribution of pRF genes across other rickettsiae, as 10 pRF genes (or inactive derivatives) also occur in AG (but not SFG) rickettsiae, with five of these genes characteristic of typical plasmids. Detailed characterization of pRF genes resulted in two novel findings: the identification of oriV and replication termination regions, and the likelihood that a second proposed plasmid, pRFdelta, is an artifact of the original genome assembly. CONCLUSION/SIGNIFICANCE Altogether, we propose a new rickettsial classification scheme with the addition of a fourth lineage, transitional group (TRG) rickettsiae, that is unique from TG and SFG rickettsiae and harbors genes from possible exchanges with AG rickettsiae via conjugation. We offer insight into the evolution of a plastic plasmid system in rickettsiae, including the role plasmids may have played in the acquirement of virulence traits in pathogenic strains, and the likely origin of plasmids within the rickettsial tree.
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Affiliation(s)
- Joseph J. Gillespie
- Virginia Bioinformatics Institute at Virginia Tech, Blacksburg, Virginia, United States of America
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Magda S. Beier
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - M. Sayeedur Rahman
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Nicole C. Ammerman
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Joshua M. Shallom
- Virginia Bioinformatics Institute at Virginia Tech, Blacksburg, Virginia, United States of America
| | - Anjan Purkayastha
- Virginia Bioinformatics Institute at Virginia Tech, Blacksburg, Virginia, United States of America
| | - Bruno S. Sobral
- Virginia Bioinformatics Institute at Virginia Tech, Blacksburg, Virginia, United States of America
| | - Abdu F. Azad
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail:
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Ogata H, Robert C, Audic S, Robineau S, Blanc G, Fournier PE, Renesto P, Claverie JM, Raoult D. Rickettsia felis, from culture to genome sequencing. Ann N Y Acad Sci 2006; 1063:26-34. [PMID: 16481487 DOI: 10.1196/annals.1355.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Rickettsia felis has been recently cultured in XTC2 cells. This allows production of enough bacteria to create a genomic bank and to sequence it. The chromosome of R. felis is longer than that of previously sequenced rickettsiae and it possess 2 plasmids. Microscopically, this bacterium exhibits two forms of pili: one resembles a conjugative pilus and another forms hair-like projections that may play a role in pathogenicity. R. felis also exhibits several copies of ankyrin-repeat genes and tetratricopeptide encoding gene that are specifically linked to pathogenic host-associated bacteria. It also contains toxin-antitoxin system encoding genes that are extremely rare in intracellular bacteria and may be linked to plasmid maintenance.
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Affiliation(s)
- H Ogata
- CNRSIBSM, Information Génomique et Structurale, Marseille, France
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Perfect JR. Cryptococcus neoformans: a sugar-coated killer with designer genes. ACTA ACUST UNITED AC 2005; 45:395-404. [PMID: 16055314 DOI: 10.1016/j.femsim.2005.06.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2005] [Accepted: 06/10/2005] [Indexed: 02/06/2023]
Abstract
Cryptococcus neoformans has become a common central nervous system pathogen as the immunocompromised populations enlarge world-wide. This encapsulated yeast has significant advantages for the study of fungal pathogenesis and these include: (1) a clinically important human pathogen; (2) a tractable genetic system; (3) advanced molecular biology foundation; (4) understanding of several virulence phenotypes; (5) well-studied pathophysiology; and (6) robust animal models. With the use of a sequenced genome and site-directed mutagenesis to produce specific null mutants, the virulence composite of C. neoformans has begun to be identified one gene at a time. Studies into capsule production, melanin synthesis, high temperature growth, metabolic pathways and a variety of signaling pathways have led to understandings of what makes this yeast a pathogen at the molecular level. Multiple principles of molecular pathogenesis have been demonstrated in virulence studies with C. neoformans. These include evolutionary differences between the varieties of C. neoformans in their genes for virulence, quantitative impact of genes on the virulence composite, species and site-specific importance of a virulence gene, gene expression correlation with its functional importance or phenotype and the impact of a pathogenesis gene on the host immune response. C. neoformans has now become a primary model to study molecular fungal pathogenesis with the goal of identifying drug targets or vaccine strategies.
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Affiliation(s)
- John R Perfect
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
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Chikamori M, Fukushima K. A new hexose transporter from Cryptococcus neoformans: molecular cloning and structural and functional characterization. Fungal Genet Biol 2005; 42:646-55. [PMID: 15907385 DOI: 10.1016/j.fgb.2005.04.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 03/28/2005] [Accepted: 04/03/2005] [Indexed: 11/22/2022]
Abstract
We carried out a screen for Cryptococcus neoformans genes involved in resistance to copper ion toxicity and identified a new hexose transporter (Hxt) gene, HXT1. Hxt1 consists of 520 amino acids and functions to transport hexoses such as glucose. Although Hxt1 conferred copper resistance to Saccharomyces cerevisiae, disruption of the HXT1 gene showed that Hxt1 is not necessary for copper resistance. In virulence tests, an hxt1 mutant strain showed 12% less phenoloxidase activity than the wild-type strain, and no difference in the ability to form melanin was identified. In addition, the hxt1 mutant strain showed virulence similar to that of the wild-type strain in experiments with Caenorhabditis elegans. However, the hxt1 mutant strain generated larger capsules than were generated by the wild-type strain. Thus, Hxt1 appears to be involved in capsule formation.
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Affiliation(s)
- Minoru Chikamori
- Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Chuo-ku, Chiba 260-8673, Japan
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Ogata H, Renesto P, Audic S, Robert C, Blanc G, Fournier PE, Parinello H, Claverie JM, Raoult D. The genome sequence of Rickettsia felis identifies the first putative conjugative plasmid in an obligate intracellular parasite. PLoS Biol 2005; 3:e248. [PMID: 15984913 PMCID: PMC1166351 DOI: 10.1371/journal.pbio.0030248] [Citation(s) in RCA: 202] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Accepted: 05/11/2005] [Indexed: 12/04/2022] Open
Abstract
We sequenced the genome of Rickettsia felis, a flea-associated obligate intracellular α-proteobacterium causing spotted fever in humans. Besides a circular chromosome of 1,485,148 bp, R. felis exhibits the first putative conjugative plasmid identified among obligate intracellular bacteria. This plasmid is found in a short (39,263 bp) and a long (62,829 bp) form. R.felis contrasts with previously sequenced Rickettsia in terms of many other features, including a number of transposases, several chromosomal toxin–antitoxin genes, many more spoT genes, and a very large number of ankyrin- and tetratricopeptide-motif-containing genes. Host-invasion-related genes for patatin and RickA were found. Several phenotypes predicted from genome analysis were experimentally tested: conjugative pili and mating were observed, as well as β-lactamase activity, actin-polymerization-driven mobility, and hemolytic properties. Our study demonstrates that complete genome sequencing is the fastest approach to reveal phenotypic characters of recently cultured obligate intracellular bacteria. Rickettsia felis is an obligate intracellular bacterium that lives in fleas and causes spotted fever in humans. Its genome sequence provides the first evidence that such bacteria can undergo conjugation.
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Affiliation(s)
- Hiroyuki Ogata
- 1 Structural and Genomic Information Laboratory, UPR 2589, IBSM, CNRS, Marseille Cedex, France
| | - Patricia Renesto
- 2 Unité des Rickettsies, UMR 6020, IFR 48, CNRS, Faculté de Médecine, Marseille Cedex, France
| | - Stéphane Audic
- 1 Structural and Genomic Information Laboratory, UPR 2589, IBSM, CNRS, Marseille Cedex, France
| | - Catherine Robert
- 2 Unité des Rickettsies, UMR 6020, IFR 48, CNRS, Faculté de Médecine, Marseille Cedex, France
| | - Guillaume Blanc
- 1 Structural and Genomic Information Laboratory, UPR 2589, IBSM, CNRS, Marseille Cedex, France
| | - Pierre-Edouard Fournier
- 1 Structural and Genomic Information Laboratory, UPR 2589, IBSM, CNRS, Marseille Cedex, France
- 2 Unité des Rickettsies, UMR 6020, IFR 48, CNRS, Faculté de Médecine, Marseille Cedex, France
| | - Hugues Parinello
- 2 Unité des Rickettsies, UMR 6020, IFR 48, CNRS, Faculté de Médecine, Marseille Cedex, France
| | - Jean-Michel Claverie
- 1 Structural and Genomic Information Laboratory, UPR 2589, IBSM, CNRS, Marseille Cedex, France
| | - Didier Raoult
- 2 Unité des Rickettsies, UMR 6020, IFR 48, CNRS, Faculté de Médecine, Marseille Cedex, France
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Lian T, Simmer MI, D'Souza CA, Steen BR, Zuyderduyn SD, Jones SJM, Marra MA, Kronstad JW. Iron-regulated transcription and capsule formation in the fungal pathogen Cryptococcus neoformans. Mol Microbiol 2005; 55:1452-72. [PMID: 15720553 DOI: 10.1111/j.1365-2958.2004.04474.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cryptococcus neoformans is the leading cause of fungal meningitis in humans. Production of a polysaccharide capsule is a key virulence property for the fungus and capsule synthesis is regulated by iron levels. Given that iron acquisition is an important aspect of virulence for many pathogens, we employed serial analysis of gene expression (SAGE) to examine the transcriptome under iron-limiting and iron-replete conditions. Initially, we demonstrated by SAGE and Northern analysis that iron limitation results in an elevated transcript level for the CAP60 gene that is required for capsule production. We also identified genes encoding putative components for iron transport and homeostasis, including the FTR1 (iron permease) gene, with higher transcript levels in the low-iron condition. An FTR1 disruption mutant grows more slowly than wild-type cells in low-iron medium, and shows delayed growth and altered capsule regulation in iron-replete medium. Iron deprivation also resulted in elevated SAGE tags for putative extracellular mannoproteins and the GPI8 gene encoding a glycosylphosphatidylinositol (GPI) transamidase. The GPI8 gene appears to be essential while disruption of the CIG1 gene encoding a mannoprotein resulted in impaired growth in low-iron medium and altered capsule response to the iron-replete condition. Additionally, we found that iron-replete conditions led to elevated transcripts for genes for iron storage, nitrogen metabolism, glycolysis, mitochondrial function, lipid metabolism and calmodulin-calcineurin signalling. Overall, these studies provide the first view of the C. neoformans transcriptional response to different iron levels.
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Affiliation(s)
- Tianshun Lian
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Agricultural Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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